Is this good practice? Joining two objects after subdivision
There isn't one right way, use what works best for you :)



You can either join objects into one object (CTRL+J) consisting of multiple meshes    
Or even join into one mesh, with all vertices manually connected (seamless)




Example
This sword is one object consisting of multiple meshes 


Easy to swap different parts 
It resembles a real sword structure which adds to realism